High-speed adjustable multilevel light modulation

摘要

A multi-level signal is produced from an input signal using a multilevel modulation technique. The input signal is encoded with a desired level code and thermometer decoded to a latch. The latch synchronizes the decoder outputs so that identical current sources can be synchronously activated and deactivated for high-fidelity signal generation around the transition point in time. The current sources are identical circuits with adjustable current settings. The adjustable current sources can be of fixed values as determined by simple electronic circuits (e.g., a resistor circuit) or be adjusted by low-speed high-resolution digital-to-analog converters. These adjustable current settings allow for the current step between levels to be adjusted as required for linearization or as desired for other system considerations. The outputs of the adjustable current sources can be added together to form a multilevel modulated output, whereby each level in the modulated signal is independently adjustable.